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1 Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA; 2 Department of Biochemistry and Molecular Biology, Uniformed Service University of the Health Sciences, Bethesda, Maryland 20184, USA
The HOP2 and MND1 genes are indispensable for meiotic recombination. The products of these genes associate to form a stable heterodimeric complex that binds DNA and stimulates the recombinase activity of Rad51 and Dmc1. Here we conduct molecular studies to delineate the action mechanism of the Hop2Mnd1 complex. We present evidence to implicate Hop2 as the major DNA-binding subunit and Mnd1 as the prominent Rad51 interaction entity. Hop2Mnd1 stabilizes the Rad51single-stranded DNA (ssDNA) nucleoprotein filament, the catalytic intermediate in recombination reactions. We also show that Hop2Mnd1 enhances the ability of the Rad51ssDNA nucleoprotein filament to capture duplex DNA, an obligatory step in the formation of the synaptic complex critical for DNA joint formation. Thus, our results unveil a bipartite mechanism of Hop2Mnd1 in homologous DNA pairing: stabilization of the Rad51 presynaptic filament and duplex DNA capture to enhance synaptic complex formation.
[Keywords: DNA repair; homologous recombination; Rad51 recombinase; synaptic complex]
Received April 19, 2007; revised version accepted June 12, 2007.
E-MAIL Patrick.Sung{at}yale.edu; FAX (203) 785-6404.
Supplemental material is available at http://www.genesdev.org.
Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.1563007
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